Means for reading off angle measurements in tachymeters and other angle-measuring instruments.



S. BAALSRUD.

MEANS FOR READING OFF ANGLE MEASUREMENTS IN ,TAcIIYMETERs AND OTHERANGLE MEASURING INSTRUMENTS.

APPL|CAT|0N.FILED FEB-12.1915- Patented Apr. 16, 1918.

3 SHEETS-SHEET 1.

WITNESSES INVENTOR i V I' urol Bolqlsrud S. BAALSRUD.

MEANS FOR READING OFF ANQLE MEASUREMENTS m TACH-YMETERS AND OTHER ANGLEMEASURING INSTRUMENTS. APPLICATION FILED FEB1I2. I915.

1 ,263,353 I PatentdApr. 16, 19186 3 SHEETS-SHEET 2.

WITNESSES V VVE I 8,,BAALSRUD. MEANS FOR READING OFF ANGLE MEASUREMENTSIN TACHYMETERS AND OTHER ANGLE MEASURING INSTRUMENTS.

APPLICATION FILED FEB. l2, 19l5.

3 SHEETS-SHEET 3.

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MEANs FOR READING OFF ANGLE MEASUREMENTS IN TAcHYME'rE s 'ANn'oTHERANGLE=MEA$UBING INSTRUMENTS.

Specification of LettersjPatent. Patented Apr. 16,, 1918..

Applicationfiledlebruary 12,1915. Serial No. 7,903.

To all whom iztmag concern: I H

e. it known that. I, SIGURD BAALSRUD, a subject of the King of Norway,residing at Christiania, Norway, have invented certain new and usefulImprovements in Means for Reading Off Angle Measurements in T achymetersand other Angle-Measuring: Instruments, of which the following isaspecification.

In the present angle-measuring instruments such as tachymeters ,andtheodolites the microscopes and magnifyingglasses for reading the anglesare placed in such a way that they are very liable to be brought out oftheir proper position, are easily damaged and make the readingdiflicult, because it is" necessary, at all events as regards the reading of the horizontal angles, for the operator to move around theinstrument, and by this movement the position of the latter is easilyderanged, such moving also occasioning loss of time.

The invention here described is intended to do away with the abovementioned inconveniences and imperfections.

As. regards the means for measuring of the horizontal angles, saiddefects and inconveniences are remedied by raising the lid or cover somuch as to give room underneath it for two obj cot-tubes or magnifiersrespectively. For this purpose, the head of the pivot is adapted to forma stand for the said object-glasses or magnifiers respectively and. thelatter are placed in a horizontal position diametrically opposite eachother and directed toward the center-line of the instrument; in thecenter two rectangular prisms are mounted at an angle of 90 degrees,which deflect the rays of light at a right angle to the axis of theobject-glasses, and in the line of the deflected rays a prism is placedwhich deflects the rays to a common ocular tube.

Further the base-plate of the instrument is provided with an up-turnededge so as to provide a cylindrical surface for placing the divisionlines. The latter will then be parallel instead of concentric, as atpresent, whereby the reading off is facilitated.

With regard to the means for reading the vertical angles, thearrangement is made, that the division lines are placed on the side ofthe circle disk turning toward the telescope, and the reading offmicroscope for reading it off is, or both microscopes if two be used,are placed upon the tube of the telescope, the latter as well as theocular tube being perforated or slottedso that the rays of light maycrossthe axial line of the telescope. The axis of the microscope whichlies next to the ocular end of the telescope is deflected by. arectangular prism, sotha-t the eye piecesof'the microscope comes besidethatv of thevtelescope, and: thus also. in'this case thereadi ngofl canbe done from the sighting stand point of the operator; only when bothmiscroscopes are used is 'itnecessary for the operator to changeposition;

The invention is explained by the accompanying drawings on which Figure1 shows a plan of the instrument with the cover removed.

Fig. 2 shows a vertical section on the line A-B in Fig. 1.

Fig. 3 shows a vertical section on the line C-D in Fig. 1.

Fig. 4 shows a detail.

Fig. 5 shows plan view, partly section, of a telescope, with microscopesfor reading vertical angles.

In Figs. 1, 2 and 3' the reference 1 indicates the vertical divisionsurface of the horizontal circle, 2 is a reflector which projects therays entering through n opening 3 in the cover 4.- onto the divisionsurface in order to give it light. 5 is two microscopes, which are fixedto the pivot of the instrument. Said pivot is, for this purpose, adaptedto form a stand for the two object tubes and for angular prisms 6 and 7placed in the center. At right angles to the axis of the two objecttubes a prism 8 is fixed to a bracket 9 attached to the pivot of theinstrument in such wise that said prism, 8 receives the rays from thetwo prisms 6 an 7 and sends them to an ocular tube 10, mounted on thesame bracket, and in the ocular llthe division bars appear'like twoimages one above the other, see Fig. ,4.

The ocular tube 10 projects through a corresponding aperture in thecover 4:. I

By the construction described above the more delicate parts of theinstrument are stored entirely away, so that they can neither be damagednor be deranged; it is only the less delicate ocular tube that is at allexposed.

In Fig. 5 12 is the vertical circle, the divisions of which are on thesurface facing the telescope. 13 is the microscope nearest the eye pieceof the telescope, said microthat of the telescope. In order to be ableto read off from the sighting point, the microscopes axis is deflectedby a prism 16 and the ocular tube 17 is placed alongside that of thetelescope.

If yet another microscope 18 is required, it is placed on the telescopetube in a similar manner to the one above described, but the ocular tubeis applied without any deflection of its axis.

By this arrangement greater safety for the microscopes is attained, theybeing less exposed to injury and not being liable to derangement, andmoreover the great advantage is gained that the division circle can bemade larger than at present. 7

Claim: 7

In an instrument for measuring angles, in

combination, a stand; a circular member supported thereby andpresentinga vertical surface; a scale upon said surface; light reflecting meansfor said scale; a pivot on said stand; two diametricallyopposedmicroscopes supported by said pivot and having their outer ends directedtoward said scale; two rectangular triangular prisms supported by saidpivot between the inner ends of said microscopes, to reflect the twoimages from said microscopes at right anglesto the latters axis; anocular supported by said pivot; and a third prism to reflect said twoimages to said ocular, said microscopes, prisms, scale and lightreflecting means being inclosed to protect them from injury.

In testimony whereof I affix my signature in presence of two witnesses.

SIGURD BAALSRUD. Witnesses: I

N. G. TANDBERG,

M. GU'rHoMsEY.

@opies of this patent may be obtained for five cents each, by addressingthe Commissioner. of Patents,

Washington, D. G. I 1

